Easiest Way of Deteriming Diff Gearing Ratio

ArmArak

ArmArak

New member
Happy 2022 3rd Gen Folks.

Here's the easiest way to determine your trucks differential ratio (no tools required other than a smartphone and a buddy.

Just place the phone on the frame's center crossmember with camera facing directly at the driveshaft and hit record. Have someone stand outside and record (or just count) as you drive straight for ten tire rotations. Remove the phone and count the driveshaft rotations.

Divide the final driveshaft count by ten to determine your diff ratio.

This took me about 3 minutes and didn't require jacking up the car or any other tools.

Just make sure you drive straight all the way to ensure the tires don't spin at different rates.

Here's a video of what mine looked like: Determining Differential Gearing Ratio - YouTube

Turns out I have a 4.1 diff as I expected so looks like I gotta find a locking 4.1 3rd member from a Tacoma :ohwell:
 
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You probably already know this, but the gearing it came with from the factory is encoded on the door jamb sticker. This particular link might not be the best example, but you'll get the idea where to look and if you scroll down they cover our era sticker and codes:

Edit - I deleted the LC Engineering link in favor of this one from our forum - it has the codes spelled out:

Some one pinch me! 4.56 gears???

From that thread:

"3rd Gen Toyota 4Runner Axle codes:

A01A - 3.73
A02A - 3.91
A03A - 4.10
A04A - 4.30
A05A - 4.56

This applies ONLY to 96-02 4Runners"

A couple years ago when I got mine I confirmed it is 4.30, as are the vast majority of factory 4Runner E-locker units it seems. There is always some debate about whether the sticker is correct but it seems to be consistent.
 
Last edited:
Endlessblockades said:
You probably already know this, but the gearing it came with from the factory is encoded on the door jamb sticker. This particular link might not be the best example, but you'll get the idea where to look and if you scroll down they cover our era sticker and codes:

Edit - I deleted the LC Engineering link in favor of this one from our forum - it has the codes spelled out:

Some one pinch me! 4.56 gears???

From that thread:

"3rd Gen Toyota 4Runner Axle codes:

A01A - 3.73
A02A - 3.91
A03A - 4.10
A04A - 4.30
A05A - 4.56

This applies ONLY to 96-02 4Runners"

A couple years ago when I got mine I confirmed it is 4.30, as are the vast majority of factory 4Runner E-locker units it seems. There is always some debate about whether the sticker is correct but it seems to be consistent.
Click to expand...


Ya the codes made me pretty certain I had a 4.10 but I would hate to buy a matching diff and have it turn out to be the wrong one haha. I got a little worried after reading some threads where people had sets that didn’t match the codes so I wanted to make sure I was getting the right one.


Sent from my iPhone using Tapatalk
 
ArmArak said:
Turns out I have a 4.1 diff as I expected so looks like I gotta find a locking 4.1 3rd member from a Tacoma :ohwell:
Click to expand...

Out of curiosity, is your 4Runner a manual trans? My '99 manual trans factory e-locker had 4.10 gears as well. Seems like most of the 4Runner lockers you see are on automatic trans 4Runners, and are 4.30.
 
JohnMc said:
Out of curiosity, is your 4Runner a manual trans? My '99 manual trans factory e-locker had 4.10 gears as well. Seems like most of the 4Runner lockers you see are on automatic trans 4Runners, and are 4.30.
Click to expand...

No, mine is an auto without e-locker. I havn't heard of 4Runners coming with locked 4.10 diffs though, interesting.
 
ArmArak said:
Turns out I have a 4.1 diff as I expected so looks like I gotta find a locking 4.1 3rd member from a Tacoma :ohwell:
Click to expand...
Just install an ARB air locker. If I had it to do over again, I could've saved a lot of money (and better options) by getting an non-elocker 4Runner and just adding the air locker.

To get the elocker I ended up with a Limited, which has several things that I hate:
sunroof
leather seats
power seats (which fail and parts aren't available)
auto climate control (which fails, but at least can be repaired by a forum member)

Unless your rig is super low mileage, it is not a bad idea to get into the ring&pinion gears to inspect them. Is a Tacoma 3rd member even plug and play?
 
Endlessblockades said:
"3rd Gen Toyota 4Runner Axle codes:

A01A - 3.73
A02A - 3.91
A03A - 4.10
A04A - 4.30
A05A - 4.56

This applies ONLY to 96-02 4Runners"

A couple years ago when I got mine I confirmed it is 4.30, as are the vast majority of factory 4Runner E-locker units it seems. There is always some debate about whether the sticker is correct but it seems to be consistent.
Click to expand...
A04A code on my 2000 Auto with eLocker, and I've confirmed by counting that it is 4.30.
 
MountainBiker said:
Just install an ARB air locker. If I had it to do over again, I could've saved a lot of money (and better options) by getting an non-elocker 4Runner and just adding the air locker.

To get the elocker I ended up with a Limited, which has several things that I hate:
sunroof
leather seats
power seats (which fail and parts aren't available)
auto climate control (which fails, but at least can be repaired by a forum member)

Unless your rig is super low mileage, it is not a bad idea to get into the ring&pinion gears to inspect them. Is a Tacoma 3rd member even plug and play?
Click to expand...


I’ve considered going ARB, but I decided against it. One of the main reasons is I like keeping everything as OEM as possible. My rig has 98k miles and it’s pretty hard to find sub 100k trucks in condition like that.

Another thing is I don’t like that the ARB is air actuated, i prefer electronic and even more so a purely mechanical design.

The tacoma 3rd member is plug and play; but either way I don’t plan on swapping my ECU to a locking one. I’ll make my own electronic unit that taps into the abs sensor (like a field monitor) and uses an OEM switch. This way I don’t need to swap ECUs and do the blue-grey mod.

Another thing I considered is making the OEM kicker purely mechanical with a shifter in the cab. That way I don’t mess with electronics at all and am not at mercy of a finicky actuator.

Edit: forgot to mention the OEM route is much cheaper than ARB haha

Sent from my iPhone using Tapatalk
 
Last edited:
ArmArak said:
I’ve considered going ARB, but I decided against it. One of the main reasons is I like keeping everything as OEM as possible. My rig has 98k miles and it’s pretty hard to find sub 100k trucks in condition like that.

Another thing is I don’t like that the ARB is air actuated, i prefer electronic and even more so a purely mechanical design.

The tacoma 3rd member is plug and play; but either way I don’t plan on swapping my ECU to a locking one. I’ll make my own electronic unit that taps into the abs sensor (like a field monitor) and uses an OEM switch. This way I don’t need to swap ECUs and do the blue-grey mod.

Another thing I considered is making the OEM kicker purely mechanical with a shifter in the cab. That way I don’t mess with electronics at all and am not at mercy of a finicky actuator.


Sent from my iPhone using Tapatalk
Click to expand...

After reading the bold comment I want to make sure you know that any 4Runner/Tacoma 8 inch factory e-locker 3rd member will require either an e-locker axle housing or modification/cutting to a normal 8 inch rear axle housing. Also the tacoma rear e-locker axle housing will not bolt right in because they are setup for leaf springs. You probably already knew all this but better to be on the safe side.
 
No ecu swap is required for an e locker, it has its own separate ecu behind the panel in the drivers footwell, many vehicles are pre wired for it and it plugs right in.
 
Bad Luck said:
After reading the bold comment I want to make sure you know that any 4Runner/Tacoma 8 inch factory e-locker 3rd member will require either an e-locker axle housing or modification/cutting to a normal 8 inch rear axle housing. Also the tacoma rear e-locker axle housing will not bolt right in because they are setup for leaf springs. You probably already knew all this but better to be on the safe side.
Click to expand...

Concur. I assumed he needed to replace a (fairly) rare 4.10 4Runner axle, not put a 4.10 locker in a non-locker axle housing.

Locker third members don't fit in non-locker axle housings, and vice versa. Different bolt patterns and an extra notch in the opening on the locker.

And Tacoma axle housings are made for leaf springs, the 4Runners for 4-link coils.

All in all, it's probably going to be easier to find a complete (more) common 4.30 4Runner axle in, along with a matching front diff. And that's not really easy, that front diff swap is a real PITA.

You might rethink that ARB thing. On-board air is nice to have if you go off roading and air down, so you can air back up when you hit pavement again. And there's nothing wrong with the Toyota e-lockers at all, but the ARB's are very nice, quick and easy to engage, easier than the e-lockers in many situations.
 
RandyBobandy said:
No ecu swap is required for an e locker, it has its own separate ecu behind the panel in the drivers footwell, many vehicles are pre wired for it and it plugs right in.
Click to expand...

That would be the easiest way - using the factory wiring and separate locker ECU. If you want to wire it directly, be aware that it's certainly not as simple as power on = locked, power off = unlocked. It needs polarity reversed and power applied to actively lock or unlock, and even then - only apply power until the limit switches show the actuator spring is moved completely (the motor runs for a second or two and tensions a spring, which then patiently waits for the locking collar to be unloaded of torque before it moves).
 
JohnMc said:
Out of curiosity, is your 4Runner a manual trans? My '99 manual trans factory e-locker had 4.10 gears as well. Seems like most of the 4Runner lockers you see are on automatic trans 4Runners, and are 4.30.
Click to expand...

My manual trans '97 also has the factory e-locker and 4:10 gearing.
 
Endlessblockades said:
You probably already know this, but the gearing it came with from the factory is encoded on the door jamb sticker. This particular link might not be the best example, but you'll get the idea where to look and if you scroll down they cover our era sticker and codes:

Edit - I deleted the LC Engineering link in favor of this one from our forum - it has the codes spelled out:

Some one pinch me! 4.56 gears???

From that thread:

"3rd Gen Toyota 4Runner Axle codes:

A01A - 3.73
A02A - 3.91
A03A - 4.10
A04A - 4.30
A05A - 4.56

This applies ONLY to 96-02 4Runners"

A couple years ago when I got mine I confirmed it is 4.30, as are the vast majority of factory 4Runner E-locker units it seems. There is always some debate about whether the sticker is correct but it seems to be consistent.
Click to expand...

I'd be very curious to see how many of those 4.56 4Runners were built/imported here, that's gotta be absurdly uncommon
 
Bad Luck said:
After reading the bold comment I want to make sure you know that any 4Runner/Tacoma 8 inch factory e-locker 3rd member will require either an e-locker axle housing or modification/cutting to a normal 8 inch rear axle housing. Also the tacoma rear e-locker axle housing will not bolt right in because they are setup for leaf springs. You probably already knew all this but better to be on the safe side.
Click to expand...


Yes, thank you! I plan on modifying my housing. I want to try and put it on my buddy’s lift and do it without even taking the axle off haha. Hope it goes well lol


Sent from my iPhone using Tapatalk
 
JohnMc said:
Concur. I assumed he needed to replace a (fairly) rare 4.10 4Runner axle, not put a 4.10 locker in a non-locker axle housing.

Locker third members don't fit in non-locker axle housings, and vice versa. Different bolt patterns and an extra notch in the opening on the locker.

And Tacoma axle housings are made for leaf springs, the 4Runners for 4-link coils.

All in all, it's probably going to be easier to find a complete (more) common 4.30 4Runner axle in, along with a matching front diff. And that's not really easy, that front diff swap is a real PITA.

You might rethink that ARB thing. On-board air is nice to have if you go off roading and air down, so you can air back up when you hit pavement again. And there's nothing wrong with the Toyota e-lockers at all, but the ARB's are very nice, quick and easy to engage, easier than the e-lockers in many situations.
Click to expand...


I am going to put a locking 4.10 in my non-locker housing. It’s really the better option for me because I don’t want to swap the front diff and I already have 4.10s. Also I am prepared to do the axle modifications, when I previously said the Tacoma diff is plug and play I meant if I already had an e-locker setup. Replacing the whole axle is another option but is coming out more expensive than I would have hoped for so just the third member is more reasonable, even tho it’ll take some more manual work from my end.


Sent from my iPhone using Tapatalk
 
RandyBobandy said:
No ecu swap is required for an e locker, it has its own separate ecu behind the panel in the drivers footwell, many vehicles are pre wired for it and it plugs right in.
Click to expand...

Is there any easy way to check if I am pre wired? I didn't think 2001 and 2002 models would have it.
 
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